I am working on a Java Client/Server that will communicate via String commands. The Server is near complete, but the Client freezes when creating the ObjectInputStream from the server. I have tried changing the I/O Streams on the server a few different ways, but no matter what I do I end up with the program freezing on the same line.
Server code:
public class Server {
//a lot of other methods
public void launchServer(){
// Text area for displaying server console
TextArea ta = new TextArea();
// Create a scene and place it in the stage
Stage console = new Stage();
Scene scene = new Scene(new ScrollPane(ta), 450, 200);
console.setTitle("Server"); // Set the stage title
console.setScene(scene); // Place the scene in the stage
console.show(); // Display the stage
new Thread( () -> {
ServerSocket serverSocket = null; Socket socket = null;
ObjectInputStream fromClient = null; ObjectOutputStream toClient = null;
Platform.runLater( () -> {
ta.appendText("Server started at " + new Date() + '\n');
});
// Create a server socket
try{
serverSocket = new ServerSocket(8000);
while (true) {
socket = serverSocket.accept();
Platform.runLater( () -> {
ta.appendText("Thread started at " + new Date() + '\n');
});
new MyThread(socket).start();
}
}
catch(IOException e){e.printStackTrace();}
}).start();
}
}
MyThread:
class MyThread extends Thread{
protected Socket socket;
private String command;
ObjectInputStream fromClient = null;
ObjectOutputStream toClient = null;
Homework6French schoolServer;
Connection connection = schoolServer.connection;
public MyThread(Socket clientSocket) {
this.socket = clientSocket;
}
public void run() {
try {
// Create data input and output streams
fromClient = new ObjectInputStream(socket.getInputStream());
toClient = new ObjectOutputStream(socket.getOutputStream());
while (true) {
//read the command from the client
command = (String) fromClient.readObject();
//read the first word of the command, and cut it out of the command
String comStart = command.substring(0, 3);
command = command.substring(4);
//run method based on what first word of command was
switch(comStart){
case "GGr":
getGrade(); break;
case "GSt":
getStudents(); break;
case "GCo":
getCourses(); break;
default:
toClient.writeChars("Command not recognized"); break;
}
}
}
catch(IOException e){e.printStackTrace();}
catch(ClassNotFoundException e){e.printStackTrace();}
finally{
try{
fromClient.close();
toClient.close();
}
catch(Exception e){e.printStackTrace();}
}
}
}
Client:
public class Client {
//member data
ObjectOutputStream toServer = null;
ObjectInputStream fromServer = null;
public void start(Stage primaryStage) {
//...
try {
// Create a socket to connect to the server
Socket socket = new Socket("localhost", 8000);
System.out.println("socket made");
// Create an input stream to receive data from the server
fromServer = new ObjectInputStream(socket.getInputStream());
System.out.println("fromSerrver made");
// Create an output stream to send data to the server
toServer = new ObjectOutputStream(socket.getOutputStream());
System.out.println("toServer made");
}
catch (IOException ex) {
ex.printStackTrace();
}
}
}
Server works fine on its own, Client launches okay and gets as far as printing "socket made", then gets stuck. Also of note is that before the try statement in the Client code, a JavaFX Stage is defined and created, and the window appears but the buttons never appear in the window.
I thought that perhaps I needed to have I/O Streams defined inside MyThread and before MyThread is called, but if I try to create an InputStream before the socket is accepted a NullPointerException is thrown. How can I understand why this InputStream freezes the client?
